1. Field of the Invention
The present invention is directed to a housing for power semiconductor modules with a base plate or for direct mounting on a heat sink.
2. Description of the Related Art
Known power semiconductor modules comprise a housing with connection elements and a substrate with power semiconductor components disposed thereon and connected appropriately in terms of circuitry, such as thyristors and/or diodes, but also power transistors such as MOSFETs or insulated gate bipolar transistors (IGBTs) with recovery diodes connected antiparallel to them.
Modern power semiconductor modules of the kind known for instance from European Patent Disclosure EP 0 750 345 A2 are therefore the point of departure of the present invention. These power semiconductor modules, with particular attention to the components essential to this invention, comprise the following:    A base of the power semiconductor module that comprises either a base plate with a substrate disposed on it, or solely a substrate;    a substrate, which has connection tracks structured appropriately for the circuitry, on which tracks semiconductor components or other components are disposed;    an at least partly framelike housing, which surrounds the substrate and in which the connection elements are embedded, for electrically connecting the components or substrate to external supply lines; and    a cap, as a top closure for the power semiconductor module.
Essentially, connection elements in power semiconductor modules have two different tasks: First, connecting the external load current supply lines to the power semiconductor components, and second, connecting external control and/or auxiliary terminals for controlling the power semiconductor components, for connecting to sensors inside the power semiconductor module, or for connecting to further components inside the power semiconductor module. Connection conductors for load currents preferably have screw connections to the external supply lines, while the external control and/or auxiliary terminals are preferably embodied as plug contacts. In the prior art, in the interior of the power semiconductor module, wire bond connections often form the electrical contact between the connection elements and the substrate connection tracks on which the components are disposed. For wire bond connection purposes, the connection elements preferably have partial surfaces that are preferably oriented parallel to the substrate but are not surrounded by the housing.
Such connection conductors are likewise disclosed in German Patent DE 43 25 942 C2, which proposes that the connection conductors be bent multiple times at an angle of less than 90° over their course inside the housing, for the sake of greater stability of the connection conductors, which are injected into the housing, to vibrations that occur in wire bonding.
It is a disadvantage of the prior art that in the references cited, the connection elements are injected into the housing. On the one hand, this means that for various configurations of connection elements, various different housings must be kept in inventory. Furthermore, the plastic shrinks during the cooling-down phase of its manufacture. As a result, the strength of the anchoring of the metal connection elements in the plastic is inadequate. Yet this strength is definitive for the quality of the wire bond connection between the partial face of the connection element and the connection tracks of the substrate, since the wire bonding, because of the vibration that is characteristic of it, requires stable supported surfaces.